package com.wyu.blog.util;

import java.text.NumberFormat;
import java.util.*;

public class RecommendUtil {

    //System.out.println("字符串\"" + str1 + "\"与\"" + str2 + "\"的比较");
    //取数组右下角的值，同样不同位置代表不同字符串的比较
    //System.out.println("差异步骤："+dif[len1][len2]);
    //相似度算法
    public static float levenshtein(String str1,String str2) {
        //计算两个字符串的长度。
        int len1 = str1.length();
        int len2 = str2.length();
        //建立上面说的数组，比字符长度大一个空间，步骤1
        int[][] dif = new int[len1 + 1][len2 + 1];
        //赋初值，步骤2
        for (int a = 0; a <= len1; a++) {
            dif[a][0] = a;
        }
        for (int a = 0; a <= len2; a++) {
            dif[0][a] = a;
        }
        //计算两个字符是否一样，计算左上的值
        int temp;
        for (int i = 1; i <= len1; i++) {
            for (int j = 1; j <= len2; j++) {
                if (str1.charAt(i - 1) == str2.charAt(j - 1)) {
                    temp = 0;
                } else {
                    temp = 1;
                }
                //取三个值中最小的
                dif[i][j] = min(dif[i - 1][j - 1] + temp, dif[i][j - 1] + 1,
                        dif[i - 1][j] + 1);
            }
        }
        //计算相似度
        float similarity = 1 - (float) dif[len1][len2] / Math.max(str1.length(), str2.length());
//        System.out.println("相似度：" + getPercentValue(similarity));
        return similarity;
    }

    //转为百分比格式
    public static String getPercentValue( float similarity) {
        NumberFormat fmt = NumberFormat.getPercentInstance();
        //最多两位百分小数，如25.23%
        fmt.setMaximumFractionDigits(2);
        return fmt.format(similarity);
    }

    //得到最小值
    private static int min(int... is) {
        int min = Integer.MAX_VALUE;
        for (int i : is) {
            if (min > i) {
                min = i;
            }
        }
        return min;
    }

    //对map中的value值进行排序
//    Map<K, V> map
    public static <K, V extends Comparable<? super V>> Map<K, V> sortDescend(Map<K,V> map) {
        List<Map.Entry<K, V>> list = new ArrayList<>(map.entrySet());
        Collections.sort(list, new Comparator<Map.Entry<K, V>>() {
            @Override
            public int compare(Map.Entry<K, V> o1, Map.Entry<K, V> o2) {
                int compare = (o1.getValue()).compareTo(o2.getValue());
                return -compare;
            }
        });

        Map<K, V> returnMap = new LinkedHashMap<K, V>();
        for (Map.Entry<K, V> entry : list) {
            returnMap.put(entry.getKey(), entry.getValue());
        }
        return returnMap;
    }


}
